Experimental Investigation of Plasma Jet Ignition Characteristics in Kerosene-Air Mixtures

Ignition and high altitude restarts under extreme conditions have always been key research problems due to low pressure and temperature of inlet air, so reliable ignition and wide ignition boundary is very necessary. In this study, the ignition characteristics of kerosene/air mixtures at different excess air coefficients with a plasma jet ignition and spark ignition were investigated experimentally in a model combustor. The plasma ignition system utilizes compressed air as plasma formation gas. The spontaneous emissions of O atoms (777 nm) and CH radicals (430 nm) were collected by photomultiplier tubes with corresponding filters to identify the ignition and combustion timing during the ignition process. A plasma jet can penetrate a recirculation zone and initiate flame kernel, and the larger plasma volume and the activated area is very helpful to achieve successful ignition. The results show that a plasma jet ignition delay time is much shorter than that for spark ignition in a wide range of excess air coefficients; the minimum plasma jet ignition delay time can be reduced by 88.74% compared to spark ignition in the same experimental conditions. With the increase in plasma arc current, the ignition delay time can be further reduced.